This study investigates what motivates people to participate in a social media campaign in the context of animal protection issues. Structural equation modeling (SEM) tested a proposed research model with survey data from 326 respondents. Situational awareness, participation benefits, and social ties influence were positive predictors of social media campaign participation intentions. Situational awareness also partially mediates the relationship between participation benefits and participation intentions as well as strong ties influence and participation intentions. When designing social media campaigns, public interest communicators should raise situational awareness and emphasize participation benefits. Messages shared through social networks, especially via strong ties, also may be more effective than those posted only on official websites or social networking sites (SNSs).